Site-specific subsoiling: benefits for Coastal Plain soils.

Abstract

The negative impacts of soil compaction on crop yields can often be alleviated by subsoiling. However, this subsoiling operation is often conducted at unnecessarily deep depths where it wastes energy and disturbs surface residue necessary for erosion control and soil quality. A corn (Zea mays L.)-cotton (Gossypium hirsutum L.) rotation experiment was conducted for four years on a Coastal Plain soil with a hardpan in east-central Alabama to evaluate the potential for site-specific subsoiling (tilling just deep enough to eliminate the hardpan layer) to improve crop yields and conserve energy. Both crops showed benefits of subsoiling as compared to the no-subsoiling treatment. Site-specific subsoiling produced yields equivalent to deep subsoiling treatment while not excessively disturbing surface soil and residues. INTRODUCTION The depth and degree of soil compaction has been found to vary greatly throughout Southern U.S. fields. Subsoiling at a uniform depth has been found to be particularly effective in reducing the effect of compaction on crop yields (Campbell et al., 1974). However, subsoiling at a depth deeper than necessary wastes subsoiling energy and unnecessarily disturbs excessive amounts of soil and crop residue. Also, subsoiling at a depth shallower than necessary wastes subsoiling energy without eliminating the compacted soil condition. Adjusting the depth of subsoiling to match the hardpan depth throughout a field, i.e., site-specific subsoiling, was investigated as a potential method for soil compaction management. Measurements of the hardpan depth taken in the Southeastern U.S. indicate that between 25 and 75% of subsoiling energy could be saved if some form of site-specific subsoiling could be developed and used (Fulton et al., 1996; Raper, 1999). Also, some data indicate that subsoiling deeper than necessary may reduce yields (Raper et al., 2000). Therefore, this study was initiated to evaluate whether the concept of site-specific subsoiling was viable. METHODS AND MATERIALS A 20-ac field from the Alabama Agricultural Experiment Station’s E.V. Smith Research and Education Center in east-central Alabama, USA was used for this experiment. The coastal plain field was comprised of a Toccoa fine sandy loam (coarse-loamy, mixed, active, nonacid, thermic Typic Udifluvents) that had excessive soil strength and required annual subsoiling. A complete set of soil cone penetrometer measurements (ASAE, 1999a; ASAE, 1999b) were obtained with the Multiple-Probe Soil Measurement System (Raper et al., 1999) on an approximate 300-ft grid. Cone index measurements were analyzed to determine depth to the hardpan over the entire field.

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